Analysis of FSS with reactance device loaded dipoles and bias feed grating-normal incidence

The resonance frequency of a frequency selective surface (FSS) consisting of dipole elements depends on the length of the dipole and the geometry of the periodic array. It may be controlled by inserting a variable reactance device into the center of each dipole; these devices operate synchronously with a common control from a bias feed grating. The grating structures are not induced by the incident electric field parallel to the dipole, but change the current distribution on the dipole as end loading, and then influence the frequency response of the FSS too. The analysis procedure for an FSS with a lumped load is the same as that of the unloaded case, if the impedance boundary conditions are employed at all loading regions. But the bias feed grating results in additional complexity, which is taken account. The grating is polarization sensitive, only the incidence with polarization parallel to the dipole is applied. The grating current is sensitive to the incident angle too; the case of normal incidence is reported.